From a0c37ceba27179496fa2f44072f85e2a5448216e Mon Sep 17 00:00:00 2001
From: Paul Fultz II <pfultz2@yahoo.com>
Date: Sat, 21 Aug 2021 14:17:05 -0500
Subject: [PATCH] Fix FP: Set correct bounds for interval (#3411)

---
 lib/valueflow.cpp      | 4 ++--
 test/testcondition.cpp | 8 ++++++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/lib/valueflow.cpp b/lib/valueflow.cpp
index 860875963..348b71ec6 100644
--- a/lib/valueflow.cpp
+++ b/lib/valueflow.cpp
@@ -4545,14 +4545,14 @@ static std::vector<ValueFlow::Value> infer(const ValuePtr<InferModel>& model,
             if (!diff.minvalue.empty()) {
                 ValueFlow::Value value(diff.minvalue.front() - 1);
                 value.setImpossible();
-                value.bound = ValueFlow::Value::Bound::Lower;
+                value.bound = ValueFlow::Value::Bound::Upper;
                 addToErrorPath(value, diff.minRef);
                 result.push_back(value);
             }
             if (!diff.maxvalue.empty()) {
                 ValueFlow::Value value(diff.maxvalue.front() + 1);
                 value.setImpossible();
-                value.bound = ValueFlow::Value::Bound::Upper;
+                value.bound = ValueFlow::Value::Bound::Lower;
                 addToErrorPath(value, diff.maxRef);
                 result.push_back(value);
             }
diff --git a/test/testcondition.cpp b/test/testcondition.cpp
index 417aab5b8..cbee6cc8a 100644
--- a/test/testcondition.cpp
+++ b/test/testcondition.cpp
@@ -3787,6 +3787,14 @@ private:
         check("bool f(bool a, bool b) { if(a && b && (!a)){} }");
         ASSERT_EQUALS("[test.cpp:1] -> [test.cpp:1]: (style) Condition '!a' is always false\n", errout.str());
 
+        check("void f(int x, int y) {\n"
+              "  if (x < y) {\n"
+              "    auto z = y - x;\n"
+              "    if (z < 1) {}\n"
+              "  }\n"
+              "}\n");
+        ASSERT_EQUALS("[test.cpp:4]: (style) Condition 'z<1' is always false\n", errout.str());
+
         check("struct a {\n"
               "  a *b() const;\n"
               "} c;\n"